This invention relates generally to refrigeration systems and, more particularly, to a method and apparatus for insulating and protecting a temperature sensor in a refrigeration system.
In air conditioning and refrigeration systems it is common to maintain a certain degree of superheat in the refrigerant passing from the evaporator to the compressor in order to protect the compressor from damage that can occur by liquid refrigerant passing therethrough. This is accomplished by using a thermal expansion valve upstream of the evaporator coil and an associated temperature sensor or bulb for sensing the temperature of the refrigerant passing from the evaporator coil.
In order for the bulb to provide accurate temperature readings, it is necessary to isolate a bulb and its connection to the outlet line such that water and air currents are not present in the area to provide an inaccurate temperature reading. This has generally been accomplished by providing some kind of protective cover over the area in which the bulb is secured to the outlet line. The most common type of insulation that is provided around the bulb is that of first using a sticky asphalt sheet called Prestite that is applied around the bulb such that no voids are present for water or air to enter into. The area is then wrapped with a tubular neoprene insulation, which is then covered with vinyl tape. Finally, the combination is covered with aluminum tape. The problems with this approach are twofold. First, the quality of the resulting insulation is dependent on the ability of the technician applying it, and there is no certainty that the process will be inadequate. Secondly, in order for the serviceman to have access to the bulb for inspection and/or maintenance purposes, it is necessary to remove each of these layers and then reapply them when the process is completed. The removal is difficult, especially the Prestite, and the reapplication results are inconsistent, as mentioned hereinabove. Both are very labor intensive and expensive.
Other types of temperature sensors are also used to sense refrigerant temperatures in various lines of a refrigeration system for purposes of control and/or protection of the system. These sensors are subject to the same problems as discussed hereinabove.